LOCALIZED L-TYPE CALCIUM CHANNELS CONTROL EXOCYTOSIS IN CAT CHROMAFFIN CELLS

被引:54
作者
LOPEZ, MG
ALBILLOS, A
DELAFUENTE, MT
BORGES, R
GANDIA, L
CARBONE, E
GARCIA, AG
ARTALEJO, AR
机构
[1] UNIV LA LAGUNA,FAC MED,UNIDAD FARMACOL,TENERIFE,SPAIN
[2] UNIV TURIN,DIPARTIMENTO ANAT & FISIOL UMANA,I-10125 TURIN,ITALY
来源
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY | 1994年 / 427卷 / 3-4期
关键词
CHROMAFFIN CELLS; CALCIUM CHANNELS; SECRETION; CA2+](I); OMEGA-CONOTOXIN GVIA; FURNIDIPINE;
D O I
10.1007/BF00374544
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Depolarizing 1-s pulses to 0 mV from a holding potential of -70 mV, induced whole-cell currents through Ca2+ channels (I-Ca) in patch-clamped cat adrenal medulla chromaffin cells. The dihydropyridine (DHP) furnidipine (3 mu M) reduced the peak current by 47% and the late current by 80%. omega-Conotoxin GVIA (CgTx, 1 mu M) reduced the peak I-Ca by 42% and the late I-Ca by 55%. Pulses (10 s duration) with 70 mM K+/2.5 mM Ca2+ solution (70 K+/2.5 Ca2+), applied to single fura-2-loaded cat chromaffin cells increased the cytosolic Ca2+ concentration ([Ca2+](i)) from 0.1 to 2.21 mu M; this increase was reduced by 43.7% by furnidipine and by 42.5% by CgTx. In the perfused cat adrenal gland, secretion evoked by 10-s pulses of 70 K+/2.5 Ca2+ was reduced by 25% by CgTx and by 96% by furnidipine. Similar results were obtained when secretion from superfused isolated cat adrenal chromaffin cells was studied and when using a tenfold lower [Ca2+](o). The results are compatible with the existence of DHP-sensitive (L-type) as well as CgTx-sensitive (N-type) voltage-dependent Ca2+ channels in cat chromaffin cells. It seems, howevever, that though extracellular Ca2+ entry through both channel types leads to similar increments of averaged [Ca2+](i), the control of catecholamine release is dominated only by Ca2+ entering through L-type Ca2+ channels. This supports the idea of a preferential segregation of L-type Ca2+ channels to localized ''hot spots'' in the plasmalemma of chromaffin cells where exocytosis occurs.
引用
收藏
页码:348 / 354
页数:7
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